Nebraska regulators approved the Keystone XL pipeline Monday, but only if it is built along a new path that may force the project developer to jump through a new set of regulatory hoops.

The 3-2 vote by the Nebraska Public Service Commission gave the green light to a different route than the one preferred by Keystone developer TransCanada, moving it east to run partially alongside the original Keystone pipeline and through a portion of the state’s ecologically sensitive Sandhills area as well across the Ogallala Aquifer.

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The Trump administration is evaluating whether it would have to re-approve the controversial pipeline to account for the new route. But activists who have spent the better part of a decade fighting to block Keystone said the decision throws the whole project into jeopardy, while TransCanada, the company seeking to build the project,said only that it is evaluating its next steps.

"This decision today throws the entire project into a huge legal question mark," said Jane Kleeb, the activist who led the opposition to the pipeline and who is now Nebraska Democratic Party chair. "TransCanada will have to go back to the State Department because that route has never been reviewed by the feds."

The State Department said it is reviewing the PSC decision for just such a possibility.

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"We won't know about any impacts until we learn precisely the extent of any changes, something we are currently engaged in," State Department spokesman Vincent Campos said.

TransCanada President and CEO Russ Girling said the company “will conduct a careful review of the Public Service Commission's ruling while assessing how the decision would impact the cost and schedule of the project."

Former President Barack Obama had blocked the permits for the pipeline in 2015, citing the oil sands' impact on climate change, but President Donald Trump quickly reversed that decision after taking office. Keystone XL is designed to transport up to 830,000 barrels per day of crude from Canada's oil sands and North Dakota's shale fields to oil refineries on the Gulf Coast.

The Nebraska PSC vote comes as TransCanada adds new crews to its cleanup operations in South Dakota, where the original Keystone Pipeline ruptured last week and released 210,000 gallons of oil. But Nebraska law bars the regulators from considering spills or pipeline safety in its decision-making process.

Environmentalists and landowners who opposed Keystone XL's construction have promised to try to overturn the commission's decision.

"We will appeal," Kleeb said. "We will challenge a foreign corporation being given eminent domain in the county courts, with every intent to bring it to the Supreme Court if needed."

Even with the approval, the project, for which costs to build the nearly 1,200 mile artery have ballooned to $8 billion, is still not ready to be built since TransCanada is gauging the economics of the huge investment. Though prices for oil have rebounded moderately in recent months, and while TransCanada has said demand for space on the pipeline is strong, it's not yet clear that enough companies will commit to the 20-year contracts required to reserve space on it.

The opposition to Keystone XL had been a rallying cry for green activists who have long said mining Canada's oil sands would be a disaster for global climate change, releasing vast amounts of carbon dioxide into the atmosphere.

But supporters have said tapping the oil fields in Alberta is no worse than the oil production in Venezuela, where much of the heavy sour crude that is shipped to U.S. refineries comes from now.

Many in the oil industry, however, no longer see the Keystone XL pipeline as crucial to the U.S. refineries as they once did, especially since the railroad sector stepped in to offer a more flexible — though more expensive — way to ship the oil.

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“There’s not going to be a parade thrown, although everyone in the industry is going to be grateful,” said Tyler Nelson, an energy lobbyist for Cornerstone Government Affairs. “It should have been done years ago. But now a lot of people want it to be over with and done and move on.”

The pipeline may struggle to succeed in the oil business. Energy markets have made the Alberta oil sands less attractive, with ExxonMobil, ConocoPhillips and others pulling out of the region to concentrate on U.S. oil shale development in Texas. Meanwhile, rival pipeline company Enbridge has expanded its pipeline system delivering Canadian crude to the U.S.

Critics have pointed to the recent shale oil boom as a reason that supply from the Canadian and North Dakota fields is in less demand, and they argue that much of the oil from Keystone XL could end up on tankers bound for export. U.S. oil production is on target to average more than 9 million barrels a day this year, nearly double what it was when TransCanada first proposed the massive pipeline.

If TransCanada gives its final approval, construction would not start until 2019 at the earliest, Paul Miller, TransCanada’s president of liquids pipelines, said during a conference call earlier this month.

The pipeline already is the focus of a court challenge stemming from Trump’s State Department approving the project. A coalition of groups is arguing the State Department did not do due diligence before approving the cross-border pipeline in March. The case is still in the beginning stages, with a decision pending from the U.S. District Court of Montana on a Trump administration motion to dismiss.